Wen's warning underscored rising concerns over lagging economic growth in rural China, home to at least two of every three Chinese. Stagnating rural incomes have created an underclass of impoverished farmers lacking affordable access to basic public services such as health care and education.

One of the greatest threats to stability stems from seizures of farmland for property development and other construction projects, Wen said the text of a speech carried in major state-run newspapers.

Disputes over compensation for land seizures have provoked thousands of protests among farmers outraged over the loss of what they view as their most fundamental asset. Incomes in rural areas average about $300 a year, compared with urban incomes of $1,000.

''In some areas, illegal seizures of farmland without reasonable compensation and resettlement have provoked uprisings,'' said Wen, the third-ranking official in the Communist Party hierarchy. ''This is still a key source of instability in rural areas and even the whole society.''

In the most recent incident, police clashing with hundreds of protesters reportedly clubbed a teenage girl to death Saturday in Sanjiao, a village in Guangdong province.

State media have denied that anyone was killed or that police used violence during the protest over land seizures. But numerous accounts by villagers and Hong Kong media reported the girl's death and said police attacked protesters with electric batons.

The violence came a month after authorities opened fire into a crowd of protesting villagers in Dongzhou, also in Guangdong province. The government said three people were killed, while villagers put the death toll at up to 20.

Such protests have grown increasingly widespread and violent in recent years, despite the central government's demand for local officials to end abuses and resolve conflicts peacefully.

Even the abolition of centuries-old farm taxes, ostensibly a huge relief for farmers barely getting by, could fail if local authorities boost so-called ''arbitrary fees,'' Wen said, referring to a wide variety of charges imposed for activities from pig raising to using rural roads.

Since taking office three years ago, China's leaders have stressed their commitment to improving incomes and living conditions for the rural population that helped bring the Communists to power in 1949.

But it is unclear how much progress has been made, given rampant corruption and vested interests at the local level, where officials can often reap huge profits from lucrative property deals.

Wen warned that such problems threaten China's ability to feed its 1.3 billion people, despite bumper harvests that raised grain production to an estimated record 484 million tons last year.

Production this year could suffer from unstable grain prices, unpredictable climate and shrinking arable land, Wen warned. He called for keeping grain prices steady, while curbing ''excessive'' increases in the prices of farming materials, such as fuel, fertilizer and seeds.

He renewed the government's promise to boost spending and improve working conditions, including protecting migrant workers who are often denied fair wages. The government must also improve rural public schools, hospitals and cultural facilities, Wen said.

''In the final analysis, we must protect the democratic rights and provide material benefits to rural citizens,'' he said. ''Improving rural quality of life and ensuring social fairness and justice are extremely important and urgent tasks.''